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Aluminum alloy is an alloy of aluminum and other elements such as copper, magnesium, zinc, silicon, etc. Aluminum alloy has the characteristics of light weight, high strength, good conductivity and excellent corrosion resistance.
Aluminum alloy is an alloy of aluminum and other elements such as copper, magnesium, zinc, silicon, etc. Aluminum alloy has the characteristics of light weight, high strength, good conductivity and excellent corrosion resistance.
Aluminum alloy
Due to these characteristics, aluminum alloys are widely used in a variety of fields such as aerospace, automobile manufacturing, construction, electronic devices and packaging materials.
Aluminum alloys are generally divided into two categories according to composition and production process:
Casting aluminum alloys: aluminum alloys suitable for casting processes, often used to make parts of complex shapes.
Deformed aluminum alloys: aluminum alloys suitable for forming by mechanical processing (such as calendering, extrusion).
Classification according to whether it can be enhanced by heat treatment:
Heat-treatable aluminum alloys: These alloys can enhance their properties by solution treatment, quenching and aging. Common series include 2xxx (aluminum-copper alloy), 6xxx (aluminum-magnesium-silicon alloy), 7xxx (aluminum-zinc alloy), etc.
These alloys are generally used in applications requiring high strength, such as aerospace and transportation.
Non-heat-treatable aluminum alloys: The strength of these alloys is primarily increased by work hardening or by adding alloying elements such as manganese and magnesium. Includes 1xxx (pure aluminum), 3xxx (aluminum-manganese alloys), 5xxx (aluminum-magnesium alloys) series.
These materials are often used in packaging, construction, and marine applications.
1xxx series aluminum alloys, also known as pure aluminum series, are mainly characterized by a high aluminum content, usually above 99%.
These alloys have some specific physical and chemical properties due to their high purity, making them very useful in specific applications.
1xxx series aluminum alloys are usually used in environments that do not require particularly high strength but require good electrical conductivity, thermal conductivity or corrosion resistance.
The microstructure of the 1xxx series aluminum alloys is mainly composed of pure aluminum crystals, which are usually large grains and have low internal stress.
Since there are almost no alloying elements, there are no significant second phases or strengthening phases.
Tensile strength: about 90-130 MPa, depending on the specific grade and work hardening state.
Ductility: 30-40%.
2xxx series aluminum alloys, commonly known as aluminum-copper alloys, use copper as the main alloying element.
This alloy series is known for its high strength and good mechanical properties, especially for the aerospace industry.
These alloys are generally used in applications that require high strength, good fatigue resistance and moderate corrosion resistance.
Although its corrosion resistance is not as good as other aluminum alloys, it can be improved by coating and special treatment.
2024: Aluminum-copper-magnesium, containing a small amount of manganese, is one of the most widely used 2xxx series alloys.
2014: Aluminum-copper-silicon-magnesium alloy, suitable for high-temperature applications.
2219: Aluminum-copper-vanadium, excellent high-temperature strength and welding performance.
Matrix phase: mainly composed of aluminum, with small amounts of copper and other alloying elements.
Strengthening phase: mainly copper-aluminum compounds (such as Al2Cu), these second phase particles are formed by aging treatment, which significantly enhances strength.
Solid solution strengthening: The copper in aluminum alloys exists mainly in the form of solid solution in the aluminum lattice.
Solid solution strengthening occurs when copper atoms dissolve in the aluminum matrix, and these copper atoms replace the positions of some aluminum atoms, thereby slightly disturbing the atomic arrangement of the crystal.
This slight lattice distortion increases the difficulty of dislocation movement, thereby increasing the yield strength and tensile strength of the material.
Precipitation strengthening: The most important strengthening mechanism in the 2xxx series alloys is achieved by the formation of precipitation phases, which are formed during the aging treatment.
The main precipitation phase is Al2Cu (called theta phase), an intermetallic compound that is very hard and brittle on a microscopic scale and can effectively hinder the movement of dislocations.
Aging process: The alloy is first heated to a certain temperature to fully dissolve the alloying elements, then rapidly cooled (quenched), and then aged (heated at a lower temperature for a period of time).
This process causes the copper in the supersaturated solid solution to gradually precipitate to form fine θ phase.
Distribution: In the early stage, the precipitates are usually dispersed in the matrix in a very fine form (called GP zone or θ” phase).
As the aging time increases, these precipitates will grow and transform into more stable θ’ and θ phases.
Grain refinement: Although the strengthening of 2xxx series alloys mainly relies on solid solution and precipitation strengthening, grain refinement can also improve the strength of the alloy to a certain extent.
Deformation during processing and subsequent annealing can be used to control the grain size.
Smaller grains can more effectively hinder the movement of dislocations, thereby improving the yield strength and fatigue resistance of the material.
Second phase particles: In addition to the main θ phase precipitates, 2xxx series alloys may also contain other types of second phase particles, such as Al2CuMg (S phase).
These particles further enhance the performance of the alloy, especially in improving the resistance to fatigue crack growth.
Tensile strength: Usually between 300 and 500 MPa, and can reach higher in certain heat treatment states.
Yield Strength: Approximately 280 to 400 MPa.
Ductility: 3-18%.
Stress Corrosion Cracking (SCC): 2xxx series aluminum alloys are particularly susceptible to stress corrosion, especially in certain environments, such as chloride-containing environments.
Fatigue Rupture: Under cyclic stress, fatigue rupture may occur, especially in aerospace applications.
Creep: Some alloys may exhibit creep when in service for a long time at high temperatures.
3xxx series aluminum alloys, also known as aluminum-manganese series, are non-heat-treatable aluminum alloys that are strengthened by adding manganese.
This alloy series is widely used in various fields for its good corrosion resistance, processability and moderate strength.
3104 aluminum for cans
3xxx series alloys are generally used in environments that require good corrosion resistance and moderate strength.
They are suitable for mild to moderate chemical and oxidizing environments and can withstand humid and changing climatic conditions.
Matrix phase: The main body is aluminum, and trace amounts of manganese, magnesium and other elements improve its performance through solid solution strengthening.
Strengthening phase: Unlike the 2xxx and 7xxx series, the 3xxx series does not rely on obvious precipitation phases to enhance strength.
Manganese mainly exists in the form of solid solution strengthening and grain refinement, improving the strength and corrosion resistance of the alloy.
Solid solution strengthening: In the 3xxx series alloys, manganese mainly acts through the solid solution strengthening mechanism.
Manganese atoms dissolve in the aluminum lattice and slightly disturb the arrangement of aluminum atoms.
Although this disturbance is small, it is enough to hinder the movement of dislocations, thereby enhancing the mechanical strength of the material.
Grain refinement: The addition of manganese also helps to refine the grains.
Grain refinement is achieved by controlling the growth of grains during solid state deformation and subsequent heat treatment of aluminum alloys.
Small grains can more effectively hinder the movement of dislocations and increase the yield strength and fatigue resistance of the alloy.
Grain refinement is achieved by controlling the cold working and annealing conditions of the alloy.
Second Phase: Although 3xxx series aluminum alloys do not rely on complex precipitation strengthening processes, the presence of manganese can form tiny second phase particles, which are usually Al(Mn,Fe)Si phases.
These second phase particles are usually uniformly distributed in the aluminum matrix, helping to prevent dislocation movement and provide additional strengthening.
These particles are mainly formed during the melting and casting of the alloy, and are further refined and uniformly distributed during subsequent heat treatment and processing.
Dislocation Structure: Because 3xxx series aluminum alloys usually undergo a certain degree of cold working, their dislocation structure is also relatively complex.
Cold working increases the dislocation density within the material, thereby increasing its strength.
However, this also reduces the ductility of the material, so annealing is usually required to restore its ductility.
Tensile Strength: Typically between 145 and 290 MPa.
Yield Strength: Approximately 90 to 200 MPa.
Ductility: 10-25%.
Common Failure Factors
Corrosion: While the 3xxx series has good corrosion resistance, long-term exposure in extreme or more aggressive chemical environments may still lead to corrosion.
Fatigue: Under repeated stress, fatigue failure may be experienced, especially in areas of stress concentration.
Stress Corrosion Cracking (SCC): Under certain circumstances, although uncommon, the 3xxx series has the potential to experience stress corrosion cracking.
4xxx series aluminum alloys are mainly based on silicon as the main alloying element.
This alloy series is particularly suitable for welding materials and castings.
The addition of silicon significantly reduces the melting point of aluminum, enhances fluidity, and also improves wear resistance.
Welding materials: used as welding rods and welding wires, suitable for the welding process of aluminum alloys.
Castings: used to manufacture automotive parts, machine parts and other casting products that require high wear resistance.
Heat sink materials: In the electronics industry, used to make heat sinks and radiators.
Service conditions
These alloys are usually used in environments that require good heat resistance and wear resistance, and are usually used as casting materials, requiring good fluidity and low thermal expansion coefficient.
4043: The silicon content is about 5%, which is one of the most commonly used welding alloys.
4032: The silicon content is as high as 12%, usually used to manufacture high-performance pistons and other mechanical parts.
Matrix phase: Aluminum alloy matrix, containing a certain proportion of silicon.
Strengthening phase: Silicon particles, usually in dispersed form, provide a certain strengthening effect, increase the hardness and wear resistance of the material.
Tensile strength: about 100 to 350 MPa, depending on the specific alloy composition and heat treatment state.
Yield strength: about 50 to 250 MPa.
Ductility: Elongation is generally between 5% and 25%, depending on the silicon content and heat treatment state.
Alloys with high silicon content (such as 4032) have lower ductility, usually below 5%, while alloys with low silicon content (such as 4043) have better ductility, which can reach more than 20%.
Hot cracking: During casting and welding, hot cracking may occur due to the presence of silicon changing the thermal properties of the alloy.
Wear: Although silicon improves wear resistance, the alloy may still experience wear under high loads.
Corrosion: In certain environments, such as salt water environments, aluminum silicon alloys may be more susceptible to corrosion than other aluminum alloy series.
5xxx series aluminum alloys, with magnesium as the main alloying element, are widely regarded as alloys with excellent corrosion resistance, high strength and good welding properties.
These characteristics make 5xxx series alloys particularly suitable for use in marine environments and applications requiring high corrosion resistance.
Marine applications: ship structures, offshore platforms, and other equipment requiring resistance to salt water corrosion.
Transportation: automobile bodies, railway carriages, truck carriages and trailers.
Construction: roof covering materials, exterior wall cladding and window frames.
Pressure vessels: used to manufacture pressure vessels and storage tanks that require no welding defects.
These alloys are generally used in environments requiring good corrosion resistance, medium to high strength and excellent welding properties, especially in marine and humid climates.
5052: Contains about 2.5% magnesium and is widely used in the manufacture of ship and vehicle parts.
5083: Contains 4.0%-4.9% magnesium. It is one of the strongest non-heat-treatable aluminum alloys and is often used in ships and other high-strength applications.
5754: Contains about 3% magnesium, has good weldability, and is commonly used in the automotive industry.
Matrix phase: Mainly aluminum, followed by magnesium. Solid solution of magnesium in aluminum provides solid solution strengthening.
Strengthening phase: Unlike the 2xxx or 7xxx series, the 5xxx series does not rely on visible precipitation phases to provide strengthening.
Strengthening mainly comes from solid solution strengthening of magnesium and grain refinement.
Tensile strength: About 100 to 350 MPa, depending on the specific grade and heat treatment state of the alloy.
Yield strength: About 50 to 250 MPa.
Ductility: Elongation is usually between 12% and 25%.
Stress corrosion cracking (SCC): Although the corrosion resistance of the 5xxx series is very good, stress corrosion cracking may still occur in some environments (especially high temperature and high stress environments).
Fatigue: Fatigue can be a problem in applications with cyclic loading, such as vehicle body and structural components.
Corrosion: Although generally very corrosion resistant, localized corrosion may occur in extremely corrosive environments or due to improper control of alloying elements such as iron and silicon.
6xxx series aluminum alloys are a widely used series of aluminum alloys, mainly with magnesium and silicon as the main alloying elements.
The alloys in this series have good mechanical properties, excellent corrosion resistance and excellent extrudability, making them a popular choice for construction and industrial applications.
Construction: used for building structural parts, door and window frames, curtain wall systems, etc.
Automotive industry: used for automotive body structural parts, radiators, car frames, etc.
Aerospace: Although not as common as 7xxx or 2xxx series, it is used in some non-structural applications.
Industrial applications: various types of machine parts, electronic equipment housings and transportation tracks.
6000 series for auto
These alloys are generally used in environments that require moderate strength and high corrosion resistance, and also require good processability and weldability.
6061: Contains about 1.0% magnesium and about 0.6% silicon.
It is one of the most versatile 6xxx series alloys and is widely used in structural applications.
6063: Contains about 0.45%-0.9% magnesium and about 0.2%-0.6% silicon.
It is widely used in building profiles and window frames and has good surface treatment characteristics.
6082: Contains about 0.6%-1.2% magnesium and about 0.7%-1.3% silicon.
It contains slightly more magnesium and silicon than 6061 and is often used in applications requiring higher strength.
Matrix phase (aluminum matrix): The matrix of the 6xxx series alloys is mainly aluminum, in which magnesium and silicon are the main alloying elements to enhance the material properties through the solid solution strengthening mechanism.
The solid solution treatment is usually carried out at high temperature, so that magnesium and silicon are completely dissolved in aluminum to form a uniform solid solution.
Solid solution strengthening: Magnesium and silicon atoms dissolve in the aluminum lattice, increasing the distortion energy of the crystal structure, which hinders the movement of dislocations, thereby improving the yield strength and tensile strength of the material.
Precipitation strengthening: The main strengthening mechanism of the 6xxx series alloys is achieved by forming a Mg2Si precipitation phase.
These precipitates are formed during the aging process of the alloy, which greatly improves the mechanical properties of the alloy.
Aging process: It includes rapid cooling after dissolution treatment to form a supersaturated solid solution, followed by aging at medium temperature to precipitate supersaturated magnesium and silicon to form fine Mg2Si precipitates, which usually appear in very fine form and are distributed in the aluminum matrix.
These fine precipitates are evenly distributed in the aluminum matrix, effectively hindering the movement of dislocations.
Grain size: By controlling the cooling rate and heat treatment parameters of the alloy, the size and morphology of the grains can be optimized, thereby further improving the mechanical properties and fatigue resistance of the material.
Tensile strength: About 240 to 320 MPa, depending on the specific alloy and heat treatment state.
Yield strength: About 140 to 290 MPa.
Ductility: The elongation is generally between 8% and 16%.
Stress corrosion cracking (SCC): Under certain stress and corrosion environments, 6xxx series alloys may experience stress corrosion cracking.
Fatigue: In applications with cyclic loading, 6xxx series alloys may experience fatigue problems, especially if not properly heat treated or designed.
Corrosion: Although corrosion resistance is good, corrosion problems may occur in extreme or more corrosive environments, such as marine salt spray environments.
7xxx series aluminum alloys are a high-strength aluminum alloy series, mainly composed of zinc as the main alloying element, and usually also contain magnesium and copper, which give these alloys excellent mechanical properties and good fatigue resistance.
These characteristics make 7xxx series aluminum alloys particularly popular in the aerospace and military fields.
Aerospace: used for aircraft structural parts, helicopter parts, rockets and spacecraft components.
Military: manufacture armor plates and other structural parts for military vehicles.
High-performance sports equipment: such as bicycle frames, rock climbing equipment and golf club heads.
Industrial Applications: high-performance molds and mechanical parts.
These alloys are generally used in environments that require extremely high strength, good fatigue resistance and moderate corrosion resistance.
7075: Contains about 5.6% zinc, about 2.5% magnesium, and about 1.6% copper.
It is the most famous alloy in the 7xxx series and is widely used due to its excellent comprehensive properties.
7068: Considered the strongest commercial aluminum alloy, it contains about 8.4% zinc, about 2.85% magnesium, and about 1.2% copper, with higher strength and better wear resistance.
7050: Contains about 6.2% zinc, about 2.3% magnesium, and about 2.3% copper.
It is used in the aviation field and has excellent resistance to stress corrosion cracking.
Matrix phase (aluminum matrix): The main structure of the alloy, in which alloying elements such as zinc, magnesium, and copper are dissolved in the aluminum lattice through a solid solution strengthening mechanism.
Solid solution strengthening increases the lattice distortion, thereby increasing the strength of the alloy.
Strengthening phase: The main strengthening mechanism of the 7xxx series alloys is through precipitation strengthening, especially precipitates containing zinc and magnesium.
The most important strengthening phases include:
MgZn2 (ζ phase): This is the main precipitate formed during the aging process.
It is very fine and evenly distributed in the aluminum matrix, effectively hindering the movement of dislocations and greatly enhancing the strength of the alloy.
Other minor precipitates: such as Σ phase (Al2CuMg) and η phase (MgZn2), they also contribute to the properties of the alloy.
Age hardening: involves solution treatment (heating to high temperature to completely dissolve the alloy elements, and then rapidly cooling to form a supersaturated solid solution) and aging treatment (keeping the temperature at a lower temperature for a long time to promote the precipitation of elements in the supersaturated solid solution to form a tiny precipitate phase).
Supersaturated solid solution: After rapid cooling, zinc and magnesium form a supersaturated state in the aluminum lattice, which is a prerequisite for the formation of precipitate phase.
Fine precipitate phase: During the aging process, the precipitated fine MgZn2 phase is distributed in the aluminum matrix.
These precipitates greatly increase the yield strength and tensile strength of the alloy.
Tensile strength: generally between 500 and 700 MPa.
Yield strength: about 430 to 630 MPa.
Ductility: The elongation is usually between 5% and 11%.
Stress Corrosion Cracking (SCC): 7xxx series alloys are particularly sensitive to stress corrosion cracking, especially in certain corrosive environments.
Fatigue: Although they have good fatigue resistance, fatigue crack initiation and propagation are still failure factors under high cyclic loading.
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